AS5045 datasheet(16/24 Pages) AMSCO

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AS5045 12-BIT PROGRAMMABLE MAGNETIC ROTARY ENCODER

Revision 1.5

www.austriamicrosystems.com

Page 16 of 24

8.4

Analog Readback Mode

Non-volatile programming (OTP) uses on-chip zener

diodes, which become permanently low resistive when

subjected to a specified reverse current.

The quality of the programming process depends on the

amount of current that is applied during the programming

process (up to 130mA). This current must be provided by

an external voltage source. If this voltage source cannot

provide adequate power, the zener diodes may not be

programmed properly.

In order to verify the quality of the programmed bit, an

analog level can be read for each zener diode, giving an

indication whether this particular bit was properly

programmed or not.

To put the AS5045 in Analog Readback Mode, a digital

sequence must be applied to pins CSn, PROG and CLK

as shown in Figure 13. The digital level for this pin

depends on the supply configuration (3.3V or 5V; see

section 0).

The second rising edge on CSn (OutpEN) changes pin

PROG to a digital output and the log. high signal at pin

PROG must be removed to avoid collision of outputs

(grey area in Figure 13).

The following falling slope of CSn changes pin PROG to

an analog output, providing a reference voltage Vref, that

must be saved as a reference for the calculation of the

subsequent programmed and unprogrammed OTP bits.

Following this step, each rising slope of CLK outputs one

bit of data in the reverse order as during programming

(see Figure 10: Md0-MD1-Div0,Div1-Indx-Z0…Z11, ccw).

If a capacitor is connected to pin PROG, it should be

removed during analog readback mode to allow a fast

readout rate. If the capacitor is not removed the analog

voltage will take longer to stabilize due to the additional

capacitance.

The measured analog voltage for each bit must be

subtracted from the previously measured Vref, and the

resulting value gives an indication on the quality of the

programmed bit: a reading of <100mV indicates a

properly programmed bit and a reading of >1V indicates

a properly unprogrammed bit.

A reading between 100mV and 1V indicates a faulty bit,

which may result in an undefined digital value, when the

OTP is read at power-up.

Following the 18th clock (after reading bit “ccw”), the chip

must be reset by disconnecting the power supply.

Vunprogrammed

CSn

CLK

116

PROG

ProgEN

Mag

Comp

PWM

halfEN

Analog Readback Data at PROG

OutpEN

CLKAread

Prog changes to Output

Vref

PWM

Dis

Z10

Z11

tLoadProg

Internal

test bit

digital

Vprogrammed

CCW

Power-on-

Reset;

turn off

supply

Figure 13: OTP register analog read

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